The present invention relates to television transmission and, more particularly, to a novel system for increasing the vertical and/or horizontal resolution of television images, while remaining compatible with receivers utilizing present television standards.
It is highly desirable to increase the resolution of the pictures provided by present day television systems. Present standards, e.g. the NTSC standard utilized in the United States and several other countries, utilize a vertical resolution of about 525 lines for a TV signal transmitted with a maximum 6 MHz. bandwidth. While other transmission standards exist, such as the PAL, SECAM and the like standards, all present standards utilize approximately the same vertical resolution and channel bandwidth. It is known that improving vertical and/or horizontal resolution by approximately a factor of 2 will dramatically increase the perceived quality of television pictures. Hitherto, such high-resolution TV systems have required an extremely large transmitted bandwidth, typically from about 20 MHz. to about 40 MHz., which large bandwidth is too great to be used with the extensive VHF TV and CATV networks presently in operation. A second major problem is that the transmission standards utilized for previously suggested high-resolution TV systems are essentially incompatible with present-day transmission standards; the millions of TV receivers presently in existence could not provide any picture, of any quality whatsoever, if tuned to these proposed high-resolution television system signals. Furthermore, the signals from hitherto proposed high-resolution television systems cannot be easily converted to present-day standards, whereby a television station or CATV system would require a dual plant, with all of the many economic disadvantages entailed therein. It is therefore highly desirable to provide a system for transmitting high-resolution television in a manner which is also compatible with the present transmission standards, whereby present receivers can provide a picture of presently-acceptable quality, and high-resolution television (HRTV) receivers can provide higher quality pictures with increased vertical and/or horizontal resolution.